Motivated by an apparent puzzle of the light-front vacua incompatible
with the axial anomaly, we have considered the two-dimensional massles
s Schwinger model for an arbitrary interpolating angle of Hornbostel's
interpolating quantization surface. By examining spectral deformation
of the Dirac sea under an external electric field semiclassically, we
have found that the axial anomaly is quantization angle independent.
This indicates an intricate nontrivial vacuum structure present even i
n the light-front limit.